Wafer registration and overlay measurement systems and related methods

ABSTRACT

A method for measuring overlay between an interest level and a reference level of a wafer includes applying a magnetic field to a wafer, detecting at least one residual magnetic field emitted from at least one registration marker of a first set of registration markers within the wafer, responsive to the detected one or more residual magnetic fields, determining a location of the at least one registration marker of the first set registration markers, determining a location of at least one registration marker of a second set of registration markers, and responsive to the respective determined locations of the at least one registration marker of the first set of registration markers and the at least one registration marker of the second set of registration markers, calculating a positional offset between an interest level of the wafer and a reference level of the wafer. Related methods and systems are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is related to U.S. patent application Ser. No.16/122,062, filed Sep. 5, 2018, pending, the entire disclosure of whichis hereby incorporated herein by this reference.

TECHNICAL FIELD

This disclosure relates generally to wafer registration and overlaymeasurement systems and methods of achieving overlay measurements. Morespecifically, overlay measurements may be conducted using visibleregistration markers in conjunction with ferromagnetic orantiferromagnetic registration markers. Registration markers exhibitingactive responses to external magnetic stimuli may also be employed.

BACKGROUND

A photolithography apparatus is a machine that applies a desired patternonto a substrate, usually onto a target portion of a bulk semiconductorsubstrate such as a semiconductor wafer. Photolithography apparatus canbe used, for example, in the fabrication of semiconductor devices. Inthat instance, a patterning device, which is referred to in the art as amask or a reticle, may be used to generate circuit patterns to be formedon die locations from an individual material level on an active surfaceof the wafer. This pattern can be transferred onto a target portion(e.g., including part of, one, or several die locations) on the wafer(e.g., a silicon wafer). Transfer of the pattern is typically effectedvia imaging onto a layer of radiation-sensitive material (i.e.,photoresist) provided on the wafer. In general, a wafer will contain agrid of adjacent target portions corresponding to die locations that aresuccessively patterned. In lithographic processes, it is often desirableto frequently make measurements of the features (i.e., structures)created and locations thereof on the wafer, e.g., for process controland verification. Various tools for making such measurements are known,including scanning electron microscopes, which are often used to measurecritical dimension (CD), and tools to measure overlay, a measure of theaccuracy of alignment of two layers in a semiconductor device. Overlaymay be described in terms of the degree of misalignment between the twolayers, for example reference to a measured overlay of 1 nm may describea situation where two layers are laterally misaligned by 1 nm.Conventional optical methods of measuring overlay typically includeusing an optical microscope and measuring an optical spectrum and/or adiffraction pattern. Additional conventional optical methods ofmeasuring overlay typically include measuring overlay with capturedimages from an optical microscope.

Various forms of scatterometers have been developed for use in thelithographic field. These devices are configured to direct a beam ofradiation onto a target and measure one or more properties of thescattered radiation (e.g., intensity at a single angle of reflection asa function of wavelength; intensity at one or more wavelengths as afunction of reflected angle; or polarization as a function of reflectedangle) to obtain a “spectrum” from which a property of interest of thetarget can be determined. Determination of the property of interest maybe performed by various techniques. Some conventional techniques includereconstruction of a target by iterative approaches such as rigorouscoupled wave analysis or finite element methods; library searches; andprincipal component analysis.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed understanding of the present disclosure, reference shouldbe made to the following detailed description, taken in conjunction withthe accompanying drawings, in which like elements have generally beendesignated with like numerals, and wherein:

FIG. 1 illustrates a schematic diagram of a registration systemaccording to one or more embodiments of the present disclosure;

FIG. 2A is a simplified top view of a registration system andsemiconductor device having registration markers formed thereinaccording to one or more embodiments of the present disclosure;

FIG. 2B is a partial side cross-sectional view of a semiconductor devicehaving registration markers formed therein according to one or moreembodiments present disclosure;

FIG. 3 is a flow diagram of a method for determining an overlaymeasurement between a reference level and an interest level of asemiconductor device according to one or more embodiments of the presentdisclosure;

FIG. 4 is a schematic representation of a sensor oriented over anregistration marker within a semiconductor device and a scalar magnitudeof a measured magnetic field emitted by the registration markeraccording to one or more embodiments of the present disclosure;

FIG. 5 is a schematic representation of a sensor oriented over aregistration marker within a semiconductor device according to one ormore embodiments of the present disclosure;

FIG. 6 shows example measurements acquired via testing performed by theinventors;

FIG. 7 shows example measurements acquired via testing performed by theinventors;

FIG. 8 shows example measurements acquired via testing performed by theinventors;

FIG. 9 shows example measurements acquired via testing performed by theinventors;

FIG. 10 is a flow diagram of a method for determining an overlaymeasurement between a reference level and an interest level of asemiconductor device according to one or more embodiments of the presentdisclosure;

FIG. 11 is a schematic representation of a sensor oriented over aregistration marker within a semiconductor device and a scalar magnitudeof a measured magnetic field emitted by the registration markeraccording to one or more embodiments of the present disclosure;

FIG. 12 is a schematic representation of a sensor oriented over aregistration marker within a semiconductor device and a scalar magnitudeof a measured magnetic field emitted by the registration markeraccording to one or more embodiments of the present disclosure;

FIG. 13 is a flow diagram of a method for determining an overlaymeasurement between a reference level and an interest level of asemiconductor device according to one or more embodiments of the presentdisclosure; and

FIG. 14 is a schematic view of a sensor head of a registration systemaccording to one or more embodiments of the present disclosure.

DETAILED DESCRIPTION

The illustrations presented herein are not actual views of anyregistration system or any component thereof, but are merely idealizedrepresentations, which are employed to describe embodiments of thepresent invention.

As used herein, the singular forms following “a,” “an,” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise.

As used herein, the term “may” with respect to a material, structure,feature, or method act indicates that such is contemplated for use inimplementation of an embodiment of the disclosure, and such term is usedin preference to the more restrictive term “is” so as to avoid anyimplication that other compatible materials, structures, features, andmethods usable in combination therewith should or must be excluded.

As used herein, any relational term, such as “first,” “second,” “above,”“upper,” etc., is used for clarity and convenience in understanding thedisclosure and accompanying drawings, and does not connote or depend onany specific preference or order, except where the context clearlyindicates otherwise. For example, these terms may refer to orientationsof elements of a registration system and/or wafer vice in conventionalorientations. Furthermore, these terms may refer to orientations ofelements of a registration system and/or wafer as illustrated in thedrawings.

As used herein, the term “substantially” in reference to a givenparameter, property, or condition means and includes to a degree thatone skilled in the art would understand that the given parameter,property, or condition is met with a small degree of variance, such aswithin acceptable manufacturing tolerances. By way of example, dependingon the particular parameter, property, or condition that issubstantially met, the parameter, property, or condition may be at least90.0% met, at least 95.0% met, at least 99.0% met, or even at least99.9% met.

As used herein, the term “about” used in reference to a given parameteris inclusive of the stated value and has the meaning dictated by thecontext (e.g., it includes the degree of error associated withmeasurement of the given parameter, as well as variations resulting frommanufacturing tolerances, etc.).

As used herein, the term “wafer” means and includes materials upon whichand in which structures including feature dimensions of micrometer andnanometer scale are partially or completely fabricated. Such materialsinclude conventional semiconductor (e.g., silicon) wafers, as well asbulk substrates of other semiconductor materials as well as othermaterials. For the sake of convenience, such materials will bereferenced below as “wafers.” Example structures formed on suchmaterials may include, for example, integrated circuitry (active andpassive), MEMS devices, and combinations thereof.

Many details of certain embodiments are described below with referenceto semiconductor devices. The term “semiconductor device” is usedthroughout to include a variety of articles of manufacture, including,for example, individual integrated circuit dies, imager dies, sensordies, and/or dies having other semiconductor features. Embodiments ofthe apparatus and processes described below may be used to measureoverlay between level of materials comprising components of integratedcircuitry on a wafer and, thus of an individual die or dice to besingulated from the wafer. The wafer (e.g., semiconductor device forms)may be unsingulated silicon comprising die locations, or a carrier waferrepopulated with previously singulated dice. The repopulated carrierwafer can include an adhesive molding material (e.g., a flexibleadhesive), which is surrounded by a generally rigid frame having aperimeter shape comparable to that of device wafer, and laterallyseparated singulated elements (e.g., dies) surrounded by the moldingmaterial.

Some embodiments of the present disclosure include registration systemsconfigured for determining an overlay measurement (e.g., measuringoverlay) between an interest level of a wafer and a reference level ofthe semiconductor device substrate, such as a wafer or other bulksubstrate comprising semiconductor material. For example, in someembodiments the registration systems may be configured to detect andlocate a first set of registration markers within a reference level ofthe semiconductor device with ferromagnetic or anti-ferromagneticmaterials or any other material or structure capable of interacting witha magnetic field. The first set of registration markers may also becharacterized as non-visible elements of a wafer, as being detectableeven when obscured by overlying levels of material. Additionally, theregistration systems may be configured to optically detect and locate asecond set of registration markers on an interest level of the wafer. Insome embodiments, the second set of registration markers includesmarkers conventionally detectable via optical microscope imaging orscatterometry systems. The second set of registration markers may thusalso be characterized as visible elements of a wafer. The registrationsystems may be configured to apply a magnetic field to the wafer tomagnetize the first set of registration markers, or may be configuredwithout such capability and a wafer including previously magnetizedregistration markers may be employed. Moreover, the registration systemsmay detect one or more residual magnetic fields from, magnetizations of,or signals from at least one marker of the first set of registrationmarkers within the wafer, and responsive to the detected one or moreresidual magnetic fields, magnetization, or signals, the registrationsystems may determine a location of the at least one registration markerof the first set of registration markers. Additionally, the registrationsystems may visually determine a location of at least one registrationmarker of the second set of registration markers via an opticalmicroscope imaging or scatterometry system. Furthermore, based on thedetermined locations of the at least one registration marker of thefirst set of registration markers and the at least one registrationmarker of the second set of registration markers, the registrationsystems may determine calculate a positional offset (e.g., and overlaymeasurement) between the interest level and the reference level of thesemiconductor device.

FIG. 1 is a schematic view of a registration system 100 according to oneor more embodiments of the present disclosure. As shown the registrationsystem 100 may be configured as a photolithography system withadditional components as described herein, although the disclosure isnot so limited. The registration system 100 can be used to alignsemiconductor devices, determine overlay measurements of a wafer andperform registration (e.g., alignment) operations on an in-processsemiconductor wafer with respect to processing tools, and if configuredfor an additional function, for example photolithographic exposure of amaterial through a reticle, perform processes for semiconductorfabrication on the wafer. Thus it will be appreciated that the presenttechnology is not limited to registration systems per se, but is alsoapplicable to semiconductor processing tools that require accurateoverlay measurements of wafers. As a non-limiting example, the presenttechnology can also be used for proper alignment in laser cutting anddrilling tools, saws, 3-D printing tools, and other processes thatnecessitate overlay measurement between various materials (e.g., levels)of in-process wafers. For purposes of illustration, the registrationsystem 100 includes an optical microscope imaging or scatterometrysystem including an image sensor 102, an illumination source 103, acondenser lens 104, a reticle 108, an objective lens 110, and asubstrate support 112 arranged in series. As noted, some of theforegoing components enable registration system 100 to performprocessing acts. Additionally, the registration system 100 includes anadditional sensor 132 (referred to herein as “response sensor 132”) anda magnetic source 130.

As shown in FIG. 1, a controller 118 may be operatively coupled to theimage sensor 102, the illumination source 103, the condenser lens 104,the reticle 108, the objective lens 110, the substrate (e.g., wafer)support 112, the response sensor 132, and the magnetic source 130 of theregistration system 100 for monitoring or controlling the operation ofthese components. Although not shown in FIG. 1, the registration system100 may also include a substrate transport station, structural supports(e.g., a reticle support, a lens support, etc.), position sensors (e.g.,a scatterometer), an immersion hood, a support actuator (e.g., anelectric motor), and/or other suitable mechanical and/or electricalcomponents. In general, the controller 118 may be configured to controlmovement of a wafer and/or components of the registration system 100before, during, and/or after a semiconductor fabrication process. Forexample, a wafer 114 can undergo photoresist deposition, patterning viaa light source and reticle, developing, baking, cleaning, and/or othersuitable processing, and the registration system 100 may be used toalign the wafer 114 and/or tools or other components associated with theregistration system 100 before, during, and/or after these processes.

The controller 118 may include a processor 120 coupled to a memory 122and an input/output component 124. The processor 120 may include amicroprocessor, a field-programmable gate array, and/or other suitablelogic devices. The memory 122 may include volatile and/or nonvolatilemedia (e.g., ROM, RAM, magnetic disk storage media, optical storagemedia, flash memory devices, and/or other suitable storage media) and/orother types of computer-readable storage media configured to store data.The memory 122 may store algorithms for alignment, edge detection,processing data related to detected magnetic fields and detectedmagnetizations, emitting magnetic fields, filters, and shape recognitionfor execution by the processor 120. In some embodiments, the processor120 may be configured to send data to a computing device operativelycoupled (e.g., over the Internet) to the controller 118, such as aserver or personal computer. The input/output component 124 may includea display, a touch screen, a keyboard, a mouse, and/or other suitabletypes of input/output devices configured to accept input from andprovide output to an operator.

In some embodiments, the registration system 100 may utilize the imagesensor 102 to capture light reflected from a wafer and send the capturedimage data to the controller 118, where it is stored in the memory 122,processed by the processor 120, and/or sent to the input/outputcomponent 124. In some embodiments, the image sensor 102 may beconfigured to capture radiation that is not in the visible spectrum,such as UV light or infrared radiation. Alternatively, the image sensor102 may be configured to capture imaging data of a wafer in both thevisible and nonvisible radiation spectrums and send this imaging data tothe controller 118. Although not shown in FIG. 1, the image sensor 102may include a lens, aperture, image sensing component, digital signalprocessor, and analog or digital output. Although the image sensor 102is shown above the illumination source 103 in FIG. 1, in someembodiments the image sensor 102 can be spaced laterally apart from thesubstrate support 112, and a mirror can be positioned to reflect lightrepresentative of the wafer surface topography into the image sensor102.

Also shown in FIG. 1, the illumination source 103 may include anultraviolet light source (e.g., a fluorescent lamp), a laser source(e.g., an argon fluoride excimer laser), and/or other suitableelectromagnetic radiation emission sources. In certain embodiments, theillumination source 103 may be configured to produce generally coherentillumination at a single frequency. In other embodiments, theillumination source 103 may also be at least partially incoherent. Infurther embodiments, the illumination source 103 may also be configuredto generate illumination at multiple frequencies.

The condenser lens 104 and the reticle 108 may be used to project apattern of radiation onto the wafer 114. The reticle 108, for example,can include an opaque plate with lines, apertures, and/or transparenciesthat allow the radiation from the illumination source 103 to passthrough in a defined aperture pattern 109. Below the reticle 108, theobjective lens 110 can be configured to project the illumination fromthe reticle 108 onto a photoresist of the wafer 114. For example, theregistration system 100 may include the optical scanner described inU.S. Pat. No. 9,748,128, to Chao et al., issued Aug. 29, 2017.

As is discussed in greater detail below, the registration system 100 mayutilize the optical microscope imaging or scatterometry system 102 todetermine locations of registration markers (e.g., optically detectableregistration markers) on a level of interest (referred to herein as an“interest level”) of the semiconductor device (e.g., a top materiallevel of the semiconductor device overlying one or more other levels).For instance, the registration system 100 may utilize the opticalmicroscope imaging or scatterometry system 102 to determine locations ofregistration markers or other elements, such as conductive via ends, onan exposed surface of a wafer or through a transparent orsemitransparent material via conventional optical methods. Furthermore,although a specific optical microscope imaging or scatterometry system102 is described herein, the disclosure is not so limited, and theregistration system 100 may include any convention optical scanner forlocating visible registration markers and performing overlaymeasurements.

In the embodiment illustrated in FIG. 1, the registration system 100 mayutilize the response sensor 132 to determine (e.g., read) locations ofregistration markers disposed within a lower level of the wafer 114(e.g., referred to herein as a “reference level”) and send capturedlocation data to the controller 118, where it is stored in the memory122, processed by the processor 120, and/or sent to the input/outputcomponent 124. As is discussed in greater detail below, the registrationsystem 100 may utilize the response sensor 132 to detect one or moremagnetic attributes of registration markers within the reference levelof the wafer 114. In some embodiments, the registration system 100 mayutilize the response sensor 132 to detect magnetic fields emitted by theregistration markers disposed within the reference level of thesemiconductor device, and responsive to the detected magnetic fields,the registration system 100 may determine the locations of theregistration markers disposed in the reference level of thesemiconductor device, as is described in greater detail below in regardto FIGS. 3-9. In additional embodiments, the registration system 100 mayutilize the response sensor 132 to measure magnetizations of theregistration markers disposed within the reference level of thesemiconductor device, and responsive to the measured magnetizations ofthe registration markers, the registration system 100 may determine thelocations of the registration markers disposed in the reference level ofthe semiconductor device 114, as is described in greater detail below inregard to FIGS. 10-12. In yet further embodiments, the registrationsystem 100 may utilize the response sensor 132 to detect responses fromregistration markers (in this case, circuits) powered by the magneticsource 130, and based on the responses, the registration system 100 maydetermine the locations of the registration markers disposed in thereference level of the semiconductor device, as is described in greaterdetail below in regard to FIG. 13. Furthermore, the registration system100 may utilize the determined locations of the registration markerswithin the reference level of the wafer 114 and the determined locationsof the registration markers in the interest level (acquired via theoptical microscope imaging or scatterometry system) to calculate apositional offset (i.e., an overlay measurement) between the interestlevel and the reference level.

In some embodiments, the response sensor 132 may include a magneticsensor for detecting magnetic attributes of responses emitted by theregistration markers. In one or more embodiments, the response sensor132 may include a Hall Effect sensor. For instance, the response sensor132 may include a transducer that varies the transducer's output voltagein response to a detected magnetic field. In additional embodiments, theresponse sensor 132 may include one or more of a giant magnetoresistance(GMR) sensor, a tunnel magnetoresistance (TMR) sensor, anelectromagnetic radiation (EMR) sensor, or a spin hall sensor. Infurther embodiments, the response sensor 132 may include a magneticforce microscopy (MFM) probe (e.g., a magnetic force microscope). Forinstance, the response sensor 132 may include a sharp magnetized tip forscanning the registration markers, where interactions between the tipand the registration markers (e.g., deflections of the tip) are detectedand utilized to reconstruct the magnetic structure of the registrationmarkers. In some embodiments, the response sensor 132 may include one ormore of a superconducting quantum interference device (SQUID) or avibrating sample magnetometer (VSM). The operation of the responsesensor 132 is described in greater detail below in regard to FIGS. 4, 5,11, and 12.

The registration system 100 may utilize the magnetic source 130 to applya magnetic field to the wafer 114 (e.g., emit a magnetic field throughthe wafer 114) and any registration markers included within the wafer114, to magnetize the registration markers within the wafer 114, and/orto power the registration markers within the wafer 114. In someembodiments, the magnetic source 130 may include a permanent magnet. Inadditional embodiments, the magnetic source 130 may include anelectromagnet. For instance, the magnetic source 130 may include anyelectromagnet known in the art. Furthermore, in some embodiments, themagnetic source 130 may be sized and shaped for applying a magneticfield to an entirety of the wafer 114 (e.g., all the registrationmarkers within the semiconductor device 114). In other embodiments, themagnetic source 130 may be sized and shaped for applying a magneticfield to only a portion of the wafer 114 (e.g., a single registrationmarker, a group of registration markers, a region of the semiconductordevice 114, etc.). In one or more embodiments, the magnetic source 130may be disposed within a probe carrying the response sensor 132. Forinstance, the magnetic source 130 may include an inductor disposedproximate to the response sensor 132, to be used to magnetizeregistration markers in their respective locations without subjectingthe entire wafer to magnetic fields and prior to use of sensor 102 onthe probe. In other embodiments, magnetic source 130 may be omitted, andwafer 114 subjected to a magnetic source after registration markers 202are formed and before placement of wafer 114 on substrate support 112 ofregistration system 100. In further embodiments, the magnetic source 130may be carried on a probe moveable under wafer 114 in alignment with aprobe carrying sensor 102 to stimulate a response from each markeraligned between the sensor 102 and the magnetic source 130.

The substrate support 112 may be configured to carry and/or move thewafer 114. The substrate support 112, which may also be characterized asa platform or a stage, may include a vacuum chuck, a mechanical chuck,and/or other suitable supporting devices. Although not shown in FIG. 1,the registration system 100 may include at least one actuator configuredto move the substrate support 112 laterally (as indicated by theX-axis), transversely (as indicated by the Y-axis), and/or vertically(as indicated by the Z-axis) relative to the response sensor 132 and/orother components of the photo registration system 100. As used herein,the X-axis, Y-axis, and Z-axis as depicted in FIG. 1 define a Cartesianspace. In certain embodiments, the substrate support 112 can alsoinclude position monitors (not shown) such as linear encoders,configured to monitor the position of the substrate support 112 alongthe X-axis, the Y-axis, and/or the Z-axis. In addition, a rotary encodermay be employed to monitor a rotational position of the wafer about theZ-axis. Even though only one substrate support 112 is shown in FIG. 1,in certain embodiments, the registration system 100 can include two,three, or any desired number of substrate supports with structuresand/or functions that are generally similar to or different than thesubstrate support 112, so that multiple wafers may be moved into and outof alignment with the remainder of registration system 100 in anexpedited fashion. In operation, the controller 118 may be used toposition the substrate support 112 to properly align the wafer 114 withtools or other components associated with the registration system 100according to aspects of the present disclosure.

FIG. 2A is a schematic top view of a reference level 208 of a wafer 114and response sensor 132 (e.g., probe) of a registration system (e.g.,registration system 100) according to one or more embodiments of thepresent disclosure. FIG. 2B is a schematic partial side cross-sectionalview of the wafer 114 of FIG. 2A with an interest level 210 overlying areference level 208 (e.g., reference layer) according to one or moreembodiments of the present disclosure. As will be appreciated by one ofordinary skill in the art, although the interest level 210 is depictedas being immediately adjacent to (e.g., immediately on top of) thereference level 208, the disclosure is not so limited, and one or moreadditional layers (e.g., levels) may be disposed between the interestlevel 210 and the reference level 208 of the wafer 114. Referring toFIGS. 2A and 2B together, in some embodiments, the reference level 208of the wafer 114 may include a first set of registration markers 202disposed within the reference level 208 of the wafer 114, and theinterest level 210 may include a second set of registration markers 203formed in or on the interest level 210 of the wafer 114. In someembodiments, one or more additional levels may be disposed between theinterest level 210 and the reference level 208, and may include one ormore opaque and/or relatively thick materials. For clarity, the interestlevel 210 has been omitted in FIG. 2A.

In some embodiments, the first set of registration markers 202 may bedisposed within the reference level 208 of the wafer 114 in a firstpattern 204. For instance, the first set of registration markers 202 maybe oriented relative to one another in the first pattern 204 (e.g., afirst registration pattern).

In one or more embodiments, each registration marker 202 of the firstset of registration markers 202 may have a circular cross-section alonga plane parallel to an upper surface of the reference level 208 of thewafer 114. In additional embodiments, each registration marker 202 ofthe first set of registration markers 202 may have any other shapedcross-section. For example, each registration marker 202 of the firstset of registration markers 202 may have a general cuboid shape (e.g.,flat rectangle shape). Additionally, each registration marker 202 of thefirst set of registration markers 202 may have any prism shape. Infurther embodiments, each registration marker 202 of the first set ofregistration markers 202 may have a frusto-conical shape as depicted inFIG. 2B.

The first set of registration markers 202 may include ferromagneticand/or antiferromagnetic materials or any other material or structurecapable of interacting with a magnetic field. As is known in the art,ferromagnetic materials contain unpaired electrons, each with a smallmagnetic field of its own, that align readily with each other inresponse to an applied external magnetic field. The alignment of theelectrons tends to persist even after the external magnetic field isremoved, a phenomenon called magnetic hysteresis. In some embodiments,the first set of registration markers 202 may include one or more ofiron, alnico alloys (e.g., iron alloys including aluminum, nickel,and/or cobalt), bismanol (i.e., bismuth and manganese alloy), chromium(IV) oxide, cobalt, fernico alloys, ferrite, gadolinium, galliummanganese arsenide, magnadur (i.e., sintered barium ferrite), magnetite,nickel, etc. In antiferromagnetic materials, magnetic moments of atomsor molecules usually related to spins of electrons, align in a regularpattern with neighboring spins pointing in opposite directions.Antiferromagnetic materials may comprise transition metal compounds,such as oxides. Examples include hematite, chromium, iron manganese andnickel oxide.

In some embodiments, the second set of registration markers 203 may bedisposed on the interest level 210 of the wafer 114 in a second pattern205 (e.g., a second registration pattern). For instance, the second setof registration markers 203 may be oriented relative to one another inthe second pattern 205. Furthermore, as is discussed in greater detailbelow, the second pattern 205 and the second set of registration markers203 may be formed via conventional methods known in the art.

In one or more embodiments, the second set of registration markers 203may correlate to the first set of registration markers 202. For example,the first pattern 204 may be at least substantially similar to thesecond pattern 205 such that measurements between markers includedwithin the first pattern 204 and markers included within the secondpattern 205 may be used to indicate an offset between the referencelevel 208 and the interest level 210 of the wafer 114. In someembodiments, each registration marker 203 of the second set ofregistration markers 203 may have shapes similar to the shapes of theregistration markers 202 of the first set of registration markers 202 orany other conventional shapes. Furthermore, the second set ofregistration markers 203 may comprise conventional materials utilizedfor registration markers detectable and visible via conventional opticalscanners and formed by conventional methods.

First Set of Embodiments

FIG. 3 shows a schematic flow diagram of a method 300 for determining anoverlay measurement between a reference level 208 and an interest level210 of a wafer 114 according to a first set of embodiments of thepresent disclosure. As is described in greater detail below, the firstset of embodiments may include procedures that involve determininglocations of one or more registration markers 202 of the first set ofregistration markers 202 within the reference level 208 of the wafer 114at a measurement site based on magnetic fields emitted by the first setof registration markers 202, determining locations of one or moreregistration markers 203 of the second set of registration markers 203within the interest level 210 of the wafer 114 at the measurement sitevia optical methods, and based on the determined locations of the firstand second registration markers 202, 203 at the measurement site,calculating a positional offset (e.g., an overlay measurement) betweenthe interest level 210 and the reference level 208 of the wafer 114.

As is shown in FIG. 3, the method 300 may include creating a firstpattern 204 (i.e., a reference level pattern) of recesses in a surface(e.g., an upper surface) of the reference level 208 of the wafer 114 byremoving material from the reference level 208 of the wafer 114, asshown in act 302. In some embodiments, the reference level 208 may besemiconductor material of wafer 114 prior to any processing thereof toform integrated circuitry. In some embodiments, a photolithographysystem may be used to create the first pattern 204 in a surface (i.e.,an active surface) of wafer 114 via conventional lithographic processesand methods. For instance, a photolithography system may utilizephotoresist application, patterning, and development over activesurface, after which semiconductor material may be removed, as by wet ordry etching (e.g., chemical or reactive ion etching) in areas unmaskedby the photoresist. As another approach, focused ion beam processes(e.g., ion milling), etc. may be used to create the first pattern 204.The recesses are then filled with a magnetic or anti magnetic materialas described below.

In some embodiments, a conventional photolithography system may be usedto form the first pattern 204 such that resulting first set ofregistration markers 202 (described below in regard to acts 304 and 312)formed within the first pattern 204 have a particular orientation and/orgeometry. For instance, the photolithography system may be used to formthe first pattern 204 such that the registration markers 202 of thefirst set of registration markers 202 have poles (e.g., magnetic poles)disposed along a particular axis (e.g., X-axis, Y-axis, or Z-axis) ofthe Cartesian space defined above in regard to FIG. 1. Additionally, thephotolithography system may be used to form the first pattern 204 suchthat the registration markers 202 of the first set of registrationmarkers 202 have particular geometries. Furthermore, because theoriginal orientations and geometries of the first set of registrationmarkers 202 are known, the registration system may be used to determineselected orientations, geometries, and locations of the first set ofregistration markers 202. In other words, the photolithography systemmay implement known orientations, geometries, and locations of the firstset of registration markers 202.

In some embodiments, the photolithography system may form the firstpattern 204 such that longitudinal lengths of the resulting registrationmarkers 202 are at least substantially parallel to one of the X-axis,Y-axis, or Z-axis of the Cartesian space. Furthermore, thephotolithography system may form the first pattern 204 such that eachregistration marker 202 of the first set of registration markers 202 hasa common orientation.

The method 300 may also include filling recesses of the first pattern204 with ferromagnetic and/or antiferromagnetic materials or any othermaterial or structure capable of interacting with a magnetic field toform the first set of registration markers 202, as shown in act 304 ofFIG. 3. For instance, act 304 may include filling recesses of the firstpattern 204 with any of the materials described above in regard to FIGS.2A and 2B. Furthermore, recesses of the first pattern 204 may be filledvia conventional methods. For example, be blanket deposited to fillrecesses of the first pattern 204 via electroplating, electrolessplating, physical vapor deposition, chemical vapor deposition, ion beamdeposition, thin film deposition, etc. The active surface of wafer 114may then be planarized by, for example, chemical mechanicalplanarization to remove deposited material other than in the recesses.In alternative embodiments, the method 300 may not include forming oneor more recesses in the wafer 114 and then filling the one or morerecesses with magnetic material. Rather, the method 300 may includedepositing magnetic material on the wafer and patterning the magneticmaterial directly. In some embodiments, the recesses of the pattern 204may be filled to enable for greater dry etches and critical path methodof critical dimension uniformity while not effecting the registrationmarkers' 202 performance.

In some embodiments, the first set of registration markers 202 formedvia filling recesses of the first pattern 204 may includenanostructures. For example, each registration marker 202 of the firstset of registration markers 202 may have at least one dimension on thenanoscale. In additional embodiments, the first set of registrationmarkers 202 formed via filling the pattern 204 may includemicrostructures. For instance, each registration marker 202 of the firstset of registration markers 202 may have at least one dimension on themicroscale. As a non-limiting example, in one or more embodiments, aregistration marker 202 of the first set of registration markers 202 mayinclude a 500 nm×100 μm×20 μm rectangular prism registration marker. Inadditional embodiments, a registration marker 202 of the first set ofregistration markers 202 may include a 4 μm×100 μm×20 μm rectangularprism registration marker. In further embodiments, a registration marker202 of the first set of registration markers 202 may include a 500 nm×50μm×5 μm rectangular prism registration marker. In yet furtherembodiments, a registration marker 202 of the first set of registrationmarkers 202 may include a 1.5 μm×1.5 μm×250 μm pillar registrationmarker. Although specific dimensions are described herein, the first setof registration markers 202 may additionally include registrationmarkers having any conventional dimension of registration markers.

After filling recesses of the first pattern 204 with ferromagneticand/or antiferromagnetic materials or any other material or structurecapable of interacting with a magnetic field, processing of wafer 114may continue with additional semiconductor fabrication processes (e.g.,depositing overlying layers, etching processes, etc.) until an interestlevel 210 of the wafer 114 is reached, as shown in act 306 of FIG. 3.For example, one or more substrates (e.g., the interest level 210 and/oradditional overlying layers) may be formed (e.g., deposited) over thereference level 208 and the first set of registration markers 202 of thewafer 114.

Upon arriving at the interest level 210 of the wafer 114, the method 300may include forming a second set of registration markers 203 on theinterest level 210 of the wafer 114, as shown in act 308 of FIG. 3. Forexample, the registration system 100 may be used to form the second setof registration markers 203 on the interest level 210 of the wafer 114.In some embodiments, forming the second set of registration markers 203may include forming a second pattern 205 of registration markers 203 onthe interest level 210 of the wafer 114. Furthermore, the second pattern205 may correlate to (e.g., may be at least substantially the same shapeand size as) the first pattern 204 of the first set of registrationmarkers 202. For instance, every registration marker 203 of the secondpattern 205 may have a correlating registration marker 202 of the firstpattern 204. Additionally, in one or more embodiments, forming thesecond set of registration markers 203 on the interest level 210 of thewafer 114 may include forming conventional markers that can be detectedand utilized by conventional optical scanning systems ofphotolithography systems (e.g., the optical microscope imaging orscatterometry system of FIG. 1). For example, forming the second set ofregistration markers 203 on the interest level 210 of the wafer 114 mayinclude forming markers via any of the methods described in U.S. Pat.No. 7,463,367, to Bowes, issued Dec. 9, 2008, U.S. Pat. No. 8,313,877,to Chung, issued Nov. 20, 2012, and/or U.S. Pat. No. 6,822,342, toBaluswamy et al., issued Nov. 23, 2004.

As will be appreciated by one of ordinary skill in the art, in one ormore embodiments, a given registration marker 202 of the first set ofregistration markers 202 and a correlating registration marker 203 ofthe second set of registration markers 203 may not have a same shape.However, in such embodiments, at least a portion of the givenregistration marker 202 of the first set of registration markers 202correlates to at least a portion of the correlating registration marker203 of the second set of registration markers 203 within the first andsecond patterns 204, 205. For example, in some embodiments, a centerpoint (e.g., a centroid) of the given registration marker 202 of thefirst set of registration markers 202 may correlate to a center point(e.g., a centroid) of the correlating registration marker 203 of thesecond set of registration markers 203. In other words, the center pointof the of the given registration marker 202 of the first set ofregistration markers 202 may be at a same point within the first pattern204 as the center point (e.g., centroid) of the correlating registrationmarker 203 of the second set of registration markers 203 is within thesecond pattern 205. In additional embodiments, a side, edge, point, orany other feature of the given registration marker 202 of the first setof registration markers 202 may correlate to a portion of thecorrelating registration marker 203 of the second set of registrationmarkers 203 within the first and second patterns 204, 205 such that apositional offset between the given registration marker 202 of the firstset of registration markers 202 correlating registration marker 203 ofthe second set of registration markers 203 may be calculated.

Referring still to FIG. 3, when initiating an overlay measurementbetween the reference level 208 and the interest level 210 of the wafer114, the method 300 may include navigating to a measurement site, asshown in act 310 of FIG. 3. For instance, the registration system 100may navigate the response sensor 132 over the wafer 114 to a location ofa registration marker 203 of the second set of registration markers 203at a desired measurement site. For instance, the registration system 100may manipulate one or more of the response sensor 132 and the substratesupport 112 via the controller 118 via any of the manners describedabove in regard to FIG. 1 to navigate the response sensor 132 to themeasurement site of the wafer 114.

Upon navigating the response sensor 132 to the measurement site of theinterest level 210 of the wafer 114, the method 300 may include applyingan external magnetic field to the wafer 114, as shown in act 312 of FIG.3, if the first set of registration markers has not already beenmagnetized, for example after registration markers 202 have been formedand before wafer 114 is placed on substrate support of registrationsystem 100. In particular, the registration system 100 may apply anexternal magnetic field to at least one registration marker 202 of thefirst set of registration markers 202 within the reference level 208 atthe measurement site of the wafer 114. In some embodiments, theregistration system 100 may apply an external magnetic field to thewafer 114 (e.g., subject the wafer 114 to a magnetic field) via themagnetic source 130 described above in regard to FIG. 1. For example,the registration system 100 may supply a current through a coil of wirewrapped around an iron core to create an external magnetic field. Insome embodiments, the registration system 100 may supply a sufficientamount of current to create an external magnetic field having a strengthgreater than 25 Oersteds (Oe). In some embodiments, applying theexternal magnetic field to the wafer 114 is optional. For instance, theregistration markers 202 may already be magnetized or may be interactingwithin magnetic fields.

In some embodiments, the registration system 100 may apply an initialexternal magnetic field (H_(ex)) to the wafer 114 to orient vectors of aresulting magnetic field of the at least one registration marker 202 ofthe first set of registration markers 202. For instance, theregistration system 100 may apply an initial external magnetic field(H_(ex)) to the wafer 114 to rotate all domains within the at least oneregistration marker 202 of the first set of registration markers 202 tobe in known directions. As a result, and as is discussed in furtherdetail below, orienting all the domains of the at least one registrationmarker of the first set of registration markers 202 enables theregistration system 100 to determine (e.g., know, set, etc.) an expectedmagnetic field for the at least one registration marker of the first setof registration markers 202 (e.g., a magnetic field that is expected tobe emitted by the at least one registration marker 202 of the first setof registration markers 202 in response to being magnetized).Furthermore, applying the initial external magnetic field (H_(ex)) tothe wafer 114 forces the resulting magnetic field of the at least oneregistration marker 202 of the first set of registration markers 202 tobe oriented in a particular (e.g., expected) orientation and direction.

After applying the initial external magnetic field to the wafer 114, theregistration system 100 may apply an additional external magnetic fieldto the wafer 114 to at least partially magnetize the at least oneregistration marker 202 of the first set of registration markers 202within the measurement site of the wafer 114. In some embodiments, theregistration system 100 may apply the additional external magnetic fieldto the wafer 114 in a particular direction. For example, theregistration system 100 may apply the additional external magnetic fieldto the wafer 114 in plane with the wafer 114. In other words, theregistration system 100 may apply the additional external magnetic fieldto the wafer 114 along a plane that is parallel to an upper surface ofthe reference level 208 of the wafer 114. In additional embodiments, theregistration system 100 may apply the additional external magnetic fieldto the wafer 114 out of plane with the wafer 114. Put another way, theregistration system 100 may apply the additional external magnetic fieldto the wafer 114 along a plane that is perpendicular to or forming anacute angle with the upper surface of the reference level 208 of thewafer 114.

In some embodiments, a direction in which the external magnetic field isemitted through the wafer 114 may be dependent on orientation of thefirst set of registration markers 202 within the wafer 114. For example,in one or more embodiments, the registration system 100 may emit theexternal magnetic field in a direction that is parallel to orperpendicular to a direction extending from a first pole (e.g.,north-seeking pole) of a given registration marker 202 to a second pole(e.g., south-seeking pole) of the given registration marker 202 of thefirst set of registration markers 202. As mentioned briefly above, thedirection in which the external magnetic field is applied to the firstset of registration markers 202 may determine expected responses of thefirst set of registration markers 202 (e.g., expected resulting magneticfields of the first set of registration markers 202).

In one or more embodiments, the registration system 100 may only apply asingle external magnetic field to the wafer 114 to both orient thedomains of the at least one registration marker 202 of the first set ofregistration markers 202 and to magnetize the at least one registrationmarker 202 of the first set of registration markers 202. In other words,the registration system 100 may not apply a second subsequent externalmagnetic field to the wafer 114 in every embodiment.

As will be appreciated by one of ordinary skill in the art, applying anexternal magnetic field to a ferromagnetic and/or antiferromagneticmaterials may cause residual (e.g., remanent) magnetic fields to beemitted by the first set of registration markers 202 even after removingthe applied external magnetic field. For instance, the first set ofregistration markers 202 may maintain a remanence (e.g., remanentmagnetization or residual magnetism). Furthermore, because the firstpattern 204 in which the first set of registration markers 202 wasformed is known, and because the original orientation of the first setof registration markers 202 is known, the first set of registrationmarkers 202 has expected pole locations, sizes, geometries, andorientations relative to one another and within the reference level 208of the wafer 114. Referring to acts 302, 304, and 312 together, in someembodiments, the registration system 100 may create the first pattern204 and first set of registration markers 202 and may apply the externalmagnetic field to result in the poles of the first set of registrationmarkers 202 being aligned along one of the axes of the Cartesian spacedefined above (e.g., the X-axis, Y-axis, or Z-axis). As a result, thefirst set of registration markers 202 may have expected resultingmagnetic fields along the axes of the Cartesian space.

Upon applying an external magnetic field, the method 300 may includedetermining (e.g., reading) a location of at least one registrationmarker of 202 the first set of registration markers 202 within thereference level 208 of the wafer 114 at the measurement site, as shownin act 314 of FIG. 3. In some embodiments, a location of at least oneregistration marker of 202 of the first set of registration markers 202within the reference level 208 of the wafer 114 at the measurement sitemay include one or more of 1) measuring a magnitude of the magneticfield (i.e., residual magnetic field) emitted by the at least oneregistration marker 202 of the first set of registration markers 202 ina scalar form along one or more axes, as shown in act 314 a, 2)calculating a magnetic field strength of the magnetic field emitted bythe at least one registration marker 202 of the first set ofregistration markers 202 in a vector form along one or more axes, asshown in act 314 b, and ultimately, 3) determining the location of theat least one registration marker 202 of the first set of registrationmarkers 202 based on data determined in acts 314 a and/or 314 b, asshown in act 314 c. Furthermore, in some embodiments, act 312 of FIG. 3(i.e., the act of applying a magnetic field) may be repeated duringand/or between any of the actions taken in act 314 to maintain and/orrecreate magnetic fields within the at least one registration marker 202of the first set of registration markers 202.

FIG. 4 is a schematic representation 400 of at least one registrationmarker 202 of the first set of registration markers 202 within areference level 208 of a wafer 114 and a response sensor 132 of aregistration system (e.g., registration system 100) disposed over thewafer 114. Additionally, FIG. 4 shows example scalar magnitudes ofmagnetic fields detected via the response sensor 132 when passing theresponse sensor 132 over an upper surface 402 of the wafer 114 and abovethe at least one registration marker 202 of the first set ofregistration markers 202 within the wafer 114. Referring to act 314 a ofFIG. 3 and FIG. 4 together, the registration system 100 may pass theresponse sensor 132 over the upper surface 402 of the wafer 114 todetect the magnetic field emitted by the at least one registrationmarker 202 of the first set of registration markers 202 within the wafer114. In some embodiments, the registration system 100 may pass theresponse sensor 132 over the wafer 114 along one or more of the X-axis,Y-axis, and/or Z-axis of the Cartesian space defined above in regard toFIG. 1. For instance, the registration system 100 may pass the responsesensor 132 along the X-axis to detect magnitudes of the magnetic fieldemitted by the at least one registration marker 202 of the first set ofregistration markers 202 along the X-axis of the Cartesian space. Asnoted above, within the first set of embodiments, the response sensor132 may include one or more of a Hall Effect sensor, a GMR sensor, a TMRsensor, an EMR sensor, or a spin hall sensor.

In some embodiments, the registration system 100 may pass the responsesensor 132 over the upper surface 402 of the wafer 114 along multipleaxes (e.g., both the X-axis and the Y-axis) of the Cartesian space todetect magnitudes of a magnetic field emitted by the at least oneregistration marker 202 of the first set of registration markers 202 atthe measurement site of the wafer 114 along the multiple axes. In one ormore embodiments, a selected location and orientation of the at leastone registration marker 202 of the first set of registration markers 202may determine along which axes the registration system 100 passes theresponse sensor 132 to detect (e.g., search for) the magnetic fieldemitted by the at least one registration marker 202 of the first set ofregistration markers 202.

Additionally, referring to act 314 b of FIG. 3, as noted above, in someembodiments, determining a location of the at least one registrationmarker 202 of the first set of registration markers 202 within thereference level 208 of the wafer 114 at the measurement site may includecalculating the magnetic field strength of the magnetic field emitted bythe at least one registration marker 202 of the first set ofregistration markers 202 in vector form. In some embodiments, theregistration system 100 may calculate the magnetic field strength of themagnetic field emitted by the at least one registration marker 202 ofthe first set of registration markers 202 in vector form byapproximating the magnetic field as a dipole and/or surface magneticmoment. For example, FIG. 5 is a schematic representation 500 of atleast one registration marker 202 of the first set of registrationmarkers 202 disposed within a reference level 208 of the wafer 114 and aresponse sensor 132 of a registration system (e.g., registration system100) disposed over the wafer 114.

Referring to FIGS. 3 and 5 together, the registration system 100 maypass the response sensor 132 over the upper surface 402 of the wafer 114to detect the magnetic field emitted by the at least one registrationmarker 202 of the first set of registration markers 202 of the wafer 114via any of the manners described above in regard to FIG. 4. Furthermore,as will be understood by one of ordinary skill in the art, when thepoles of a registration marker 202 are closely spaced relative to anobservation distance (d), the magnetic field strength of the magneticfield emitted by the registration markers can be approximated as adipole

$\left( {\frac{1}{r^{3}}{dependence}} \right).$Additionally, when the poles of a registration marker are widely spacedrelative to the observation distance (d), the magnetic field strength ofthe magnetic field emitted by the registration markers can beapproximated by the surface magnetic moment

$\left( {\frac{1}{r^{2}}{dependence}} \right).$For instance, the magnetic field strength may be calculated via thefollowing equation:

$H_{dip} = {\frac{1}{\mu_{0}}\frac{{3\left( {m*r} \right)r} - {mr}^{2}}{r^{5}}}$

where H_(dip) is the magnetic field strength in vector form, r is thevector from the position of the dipole to the position where themagnetic field is being measured, r is the absolute value of r: thedistance from the dipole, m is the vector dipole moment, and μ₀ is thepermeability of free space.

By utilizing the response sensor 132 and responsive to passing theresponse sensor 132 over the wafer 114 along multiple axes, theprocessor 120 of registration system 100 may calculate the magneticfield strength of the magnetic field emitted by the at least oneregistration marker 202 of the first set of registration markers 202 invector form (e.g., H_(x), H_(y), and H_(z)) along one or more of theX-axis, the Y-axis, and the Z-axis of the Cartesian space. As a result,the registration system 100 may calculate a representation of themagnetic field in vectors. In some embodiments, the foregoing equationand approximations may drive the size and shape of the registrationmarkers 202 of the first set of registration markers 202 created viaacts 302, 304, and 312 of FIG. 3, and as a result, the first pattern 204formed in act 302 of FIG. 3. For instance, the size and shape of eachregistration marker 202 of the first set of registration markers 202(e.g., the pattern 204 for forming the registration markers 202) may bedesigned to have resulting magnetic poles of each registration marker202 of the first set of registration markers 202 be widely or closelyspaced such that the resulting magnetic fields can be approximatedaccording to one of the above mentioned methods.

In some embodiments, the registration system 100 may perform both acts314 a and 314 b when determining a location of a registration marker 202of the first set of registration markers 202 within the reference level208 of the wafer 114. In other embodiments, the registration system 100may perform only one of acts 314 a and 314 b when determining a locationof a registration marker 202 of the first set of registration markers202 within the reference level 208 of the wafer 114. In other words,both of acts 314 a and 314 b are not required in every embodiment of thepresent disclosure.

The following are examples of simulations performed by the inventorswithin the scope of the first set of embodiments where the magneticfield strengths of magnetic fields emitted by registration markers arecalculated.

Example 1

FIG. 6 shows testing results 600 from laboratory testing from a firstexample. Referring to FIGS. 3-6 together, in the laboratory tests, twotypes of 500 nm×100 μm×20 μm registration markers (relatively thinspecimen) were disposed within respective wafers. The first type ofregistration marker included Fe65Co35, and the second type ofregistration marker included Co20Ni80. Four registration markers of thefirst type of registration markers were disposed at varying depths (250nm, 1 μm, 3 μm, and 10 μm) within four respective wafers. Additionally,four registration markers of the second type of registration markerswere disposed at varying depths (250 nm, 1 μm, 3 μm, and 10 μm) withinfour respective wafers. All of the wafers were subjected to a magneticfield greater than 25 Oe. Furthermore, the wafers were subjected to anin plane magnetic field (e.g., magnetic field emitted in a directionparallel to a plane defined by an upper surface of a respective wafer).After subjecting the wafers to the magnetic field, the residual magneticfields of the registration markers were detected at the four correlatingdepths of the registration markers (250 nm, 1 μm, 3 μm, and 10 μm) andalong both the X-axis and the Z-axis utilizing one or more of thesensors described above. Furthermore, based on the detected magneticfields, the correlating magnetic field strengths were calculated alongboth the X-axis and the Z-axis (shown in the associated graphs of FIG.6) via one or more of the approximation methods described above.

Example 2

FIG. 7 shows testing results 700 from laboratory testing from a secondexample. Referring to FIGS. 3-5 and 7 together, in the laboratory tests,two types of 4.0 μm×100 μm×20 μm registration markers (relatively thickspecimen) were disposed within respective wafers. The first type ofregistration marker included Fe65Co35, and the second type ofregistration marker included Co20Ni80. Four registration markers of thefirst type of registration markers were disposed at varying depths (250nm, 1 μm, 3 μm, and 10 μm) within four respective wafers. Additionally,four registration markers of the second type of registration markerswere disposed at varying depths (250 nm, 1 μm, 3 μm, and 10 μm) withinfour respective wafers. All of the wafers were subjected to a magneticfield greater than 25 Oe. Furthermore, the wafers were subjected to anin plane magnetic field (e.g., magnetic field emitted in a directionparallel to a plane defined by an upper surface of a respective wafers).After subjecting the wafers to the magnetic field, the residual magneticfields of the registration markers were detected at the four correlatingdepths of the registration markers (250 nm, 1 μm, 3 μm, and 10 μm) andalong both the X-axis and the Z-axis utilizing one or more of thesensors described above. Furthermore, based on the detected magneticfields, the correlating magnetic field strengths were calculated alongboth the X-axis and the Z-axis (shown in the associated graphs of FIG.7) via one or more of the approximation methods described above.

Example 3

FIG. 8 shows testing results 800 from laboratory testing from a thirdexample. Referring to FIGS. 3-5 and 8 together, in the laboratory tests,two types of 500 nm×50 μm×5 μm registration markers (relatively thinspecimen) were disposed within respective wafers. The first type ofregistration marker included Fe65Co35, and the second type ofregistration marker included Co20Ni80. Four registration markers of thefirst type of registration markers were disposed at varying depths (250nm, 1 μm, 3 μm, and 10 μm) within four respective wafers. Additionally,four registration markers of the second type of registration markerswere disposed at varying depths (250 nm, 1 μm, 3 μm, and 10 μm) withinfour respective wafers. All of the wafers were subjected to a magneticfield greater than 25 Oe. Furthermore, the wafers were subjected to anin plane magnetic field (e.g., magnetic field emitted in a directionparallel to a plane defined by an upper surface of a respective wafers).After subjecting the wafers to the magnetic field, the residual magneticfields of the registration markers were detected at the four correlatingdepths of the registration markers (250 nm, 1 μm, 3 μm, and 10 μm) andalong both the X-axis and the Z-axis utilizing one or more of thesensors described above. Furthermore, based on the detected magneticfields, the correlating magnetic field strengths were calculated alongboth the X-axis and the Z-axis (shown in the associated graphs of FIG.8) via one or more of the approximation methods described above.

Example 4

FIG. 9 shows testing results 900 from laboratory testing from a fourthexample. Referring to FIGS. 3-5 and 9 together, in the laboratory tests,two types of 1.5 μm×1.5 μm×250 μm registration markers (specimen shapedlike a rod) were disposed within respective wafers in a directionperpendicular to EXAMPLES 1-3. The first type of registration markerincluded Fe65Co35, and the second type of registration marker includedCo20Ni80. Four registration markers of the first type of registrationmarkers were disposed at varying depths (250 nm, 1 μm, 3 μm, and 10 μm)within four respective wafers. Additionally, four registration markersof the second type of registration markers were disposed at varyingdepths (250 nm, 1 μm, 3 μm, and 10 μm) within four respective wafers.All of the wafers were subjected to a magnetic field greater than 25 Oe.Furthermore, the wafers were subjected to an out of plane magnetic field(e.g., magnetic field emitted in a direction perpendicular to a planedefined by an upper surface of a respective wafers). After subjectingthe wafers to the magnetic field, the residual magnetic fields of theregistration markers were detected at the four correlating depths of theregistration markers (250 nm, 1 μm, 3 μm, and 10 μm) and along both theX-axis and the Z-axis utilizing one or more of the sensors describedabove. Furthermore, based on the detected magnetic fields, thecorrelating magnetic field strengths were calculated along both theX-axis and the Z-axis (shown in the associated graphs of FIG. 9) via oneor more of the approximation methods described above.

Referring again to FIG. 3, based on the data acquired and/or calculatedvia one or more of acts 314 a and 314 b (e.g., scalar and/or vectorrepresentations of the magnetic field of the at least one registrationmarker 202 of the first set of registration markers 202 along axes ofthe Cartesian space), the registration system 100 may determine thelocation of the at least one registration marker 202 of the first set ofregistration markers 202 in three dimensions (e.g., in the X-axis,Y-axis, and Z-axis) within the wafer 114 at the measurement site, asshown in act 314 c of FIG. 3. In other words, in some embodiments, theregistration system 100 may determine the location of at least oneregistration marker 202 of the first set of registration markers 202 asa vector plot.

In the first set of embodiments, as is mentioned briefly above, thegeometries and original orientations and locations of the first set ofregistration markers 202 (and the at least one registration marker 202)are known, and as a result, the first set of registration markers 202have expected magnetic field profiles (e.g., three expected vectorcomponents of the magnetic field profiles). Furthermore, based on theexpected magnetic field of the at least one registration marker 202 ofthe first set of registration markers 202 and the actualmeasured/calculated magnetic fields of the at least one registrationmarker 202 of the first set of registration markers 202, theregistration system 100 may determine the actual location of the atleast one registration marker 202 of the first set of registrationmarkers 202. For instance, as will be understood by one of ordinaryskill in the art, the registration system 100 may utilize significantfeatures of known data such as, for example, known locations ofminimums, maximum, zero crossing values, and maximum derivatives of theexpected magnetic field and original orientation of the at least oneregistration marker 202 of the first set of registration markers 202within an ideal grid relative to significant features of measured and/orcalculated data such as, for example, the actual calculated and/ormeasured minimums, maximums, zero crossing values, and maximumderivatives of the detected magnetic field to determine a location(e.g., a precise location) of the at least one registration marker 202of the first set of registration markers 202 within the reference level208 of the wafer 114. As a non-limiting example, if an expected responsesignal is a sinusoidal or other periodic response (e.g., FIG. 4), theregistration system 100 may utilize the significant features of theexpected response signal and significant features of themeasured/calculated response signal to determine the actual location ofthe at least one registration marker 202 of the first set ofregistration markers 202.

In addition to determining a location of the at least one registrationmarker 202 of the first set of registration markers 202 within thereference level 208 of the wafer 114 at the measurement site, the method300 may include determining a location of at least one registrationmarker 203 of the second set of registration markers 203 on the interestlevel 210 of the wafer 114 at the measurement site, as shown in act 316of FIG. 3. For instance, the registration system 100 may utilize theoptical microscope imaging or scatterometry system described above inregard to FIG. 1 to detect the at least one registration marker 203 ofthe second set of registration markers 203 on the interest level 210 ofthe wafer 114 at the measurement site. For example, the registrationsystem 100 may detect the at least one registration marker 203 of thesecond set of registration markers 203 via any conventional opticalmethods. For example, the registration system 100 may detect the atleast one registration marker 203 of the second set of registrationmarkers 203 via any of the methods described in U.S. Pat. No. 7,463,367,to Bowes, issued Dec. 9, 2008, U.S. Pat. No. 8,313,877, to Chung, issuedNov. 20, 2012, and/or U.S. Pat. No. 6,822,342, to Baluswamy et al.,issued Nov. 23, 2004.

Upon determining the locations of the at least one registration marker202 of the first set of registration markers 202 and the at least oneregistration marker 203 of the second set of registration markers 203 atthe measurement site, the method 300 may include calculating apositional offset (e.g., an overlay measurement) between the interestlevel 210 and the reference level 208 of the wafer 114, as shown in act318 of FIG. 3. For instance, based on the locations of the at least oneregistration marker 202 of the first set of registration markers 202within the reference level 208 and the at least one registration marker203 of the second set of registration markers 203 within the interestlevel 210, the registration system 100 may be used to calculate thepositional offset via conventional methods. As a non-limiting example,the method 300 may include calculating the positional offset based ontwo registration markers via any of the methods described in U.S. Pat.No. 7,181,057, to Ghinovker et al., issued Feb. 20, 2007, U.S. Pat. No.6,779,171, to Baggenstoss, issued Aug. 17, 2004, U.S. Pat. No. 6,778,275to Bowes, issued Aug. 17, 2004, and/or U.S. Pat. No. 7,463,367, toBowes, issued Dec. 9, 2008. In additional to calculating offsets,various mathematical models may be applied to interpolate andextrapolate obtained data to generate a geometrical model of the layeroverlay.

In some embodiments, acts 310-318 of FIG. 3 may be repeated multipletimes to calculate a positional offset between the interest level 210and the reference level 208 of the wafer 114. In some embodiments, afurther set of second registration markers may be applied to a higherinterest level 210, and acts 310-318 of FIG. 3 may be repeated torecalibrate wafer alignment. Empirical data as a given batch of wafersis processed may be employed to determine with what frequency, and atwhich levels it is most useful to perform an overlay determinationaccording to the disclosure.

Additionally, the method 300 may include adjusting future semiconductorfabrication processes on the wafer 114 based on the calculatedpositional offset. For instance, the registration system 100 may be usedto adjust relative wafer and tool positions in future processes such asforming overlying material levels, patterning, etching, etc. based onthe calculated positional offset via conventional methods.

The method 300 may, optionally, include demagnetizing the registrationmarkers 202, as shown in act 314 of FIG. 3. For instance, theregistration markers 202 may be demagnetized by heating the registrationmarkers 202 past the registration markers' Curie point (i.e., thermalerasure), applying an alternating current (i.e., AC current) through theregistration markers 202, permitting self-demagnetization, etc.Demagnetization of the wafer 114 may be desirable so as to not induceartifact into performance of integrated circuitry of semiconductor dielocations during pre-singulation testing. Further, if registrationmarkers 202 are located within semiconductor die locations, so as to notinduce artifact into the performance of integrated circuitry componentsof dice singulated from the wafer 114, or into circuitry of othercomponents located in close proximity to such semiconductor dice inhigher-level packaging assemblies.

The method 300 for determining an overlay measurement between aninterest level and a reference level of a wafer described herein mayprovide advantages over conventional methods of determining overlaymeasurements. For example, because the method 300 utilizes magneticfields emitted by the first set of registration markers within thereference level to determine the locations of the first set ofregistration markers instead of optical methods, the method 300 is nothindered by opaque materials and/or thick materials overlying the firstset of registration markers or reference level, which often hinderconventional optical scanner registration systems. Furthermore, thecalculated positional offsets between interest levels and referencelevels of wafers are not influenced by surface topography of the wafer,unlike conventional registration systems. Additionally, becausedetecting the first set of registration markers is not based on opticaldetection (e.g., limited by image resolutions), the method 300 enablessmaller marker sizes in comparison to conventional registration systems.As a result, less of a wafer is required for (e.g., wasted on)registration markers. Moreover, utilizing registration markers maysimplify downstream patching requirements and may provide more accurateregistration procedures and modeling in comparison to conventionalsystems. For instance, patching requirements do not need to beconsidered for open or closed status at any one particular photo level.In particular, substrates disposed over the registration markers mayremain closed all the times. Additionally, consideration on how to openan area of wafer or whether the wafer should be opened is unnecessarybecause determining the registration markers' locations is not impactedby opacity of the substrates disposed over the registration markers. Asa result, the substrates disposed over the registration markers mayremain un-opened and ma maintain an at least substantially flattopography to alleviate other post processing topography issues that cancause non-uniformities in critical dimension patterns.

Second Set of Embodiments

FIG. 10 shows a schematic flow diagram of a method 1000 for determiningan overlay measurement between a reference level 208 and an interestlevel 210 of a wafer 114 according to a second set of embodiments of thepresent disclosure. As is described in greater detail below, the secondset of embodiments may include procedures that involve determininglocations of one or more registration markers 202 of the first set ofregistration markers 202 with the reference level 208 of the wafer 114based on measuring and/or detecting magnetizations (e.g., magnetizationforces) of one or more registration markers 202 of the first set ofregistration markers 202 within the wafer 114, determining locations ofone or more registration markers 203 of the second set of registrationmarkers 203 within the interest level 210 of the wafer 114 at themeasurement site via optical methods, and based on the determinedlocations of the first and second registration markers 202, 203 at themeasurement site, calculating a positional offset (e.g., overlaymeasurement) between the interest level 210 and the reference level 208of the wafer 114.

As shown in FIG. 10, similar to method 300 discussed above in regard toFIG. 3, the method 1000 includes creating a first pattern 204 (i.e., areference level pattern) in a surface (e.g., an upper surface) of thereference level 208 of the wafer 114 by removing material from thereference level 208 of the wafer 114, as shown in act 1002. In someembodiments, the first pattern 204 may be created via conventionallithographic processes and methods, as described above.

The method 1000 may also include filling the first pattern 204 withferromagnetic and/or antiferromagnetic materials or any other materialor structure capable of interacting with a magnetic field to form thefirst set of registration markers 202, as shown in act 1004 of FIG. 10.For instance, act 1004 may include filling recesses of the first pattern204 with any of the materials described above in regard to FIGS. 2A and2B. Furthermore, recesses of the first pattern 204 may be filled viaconventional methods. In some embodiments, the first set of registrationmarkers 202 within the reference level 208 of the wafer 114 may beformed via any of the methods described above in regard to FIG. 3.

After filling recesses of the first pattern 204 with ferromagneticand/or antiferromagnetic materials, the registration system 100 and/orother tools may continue with additional semiconductor fabricationprocesses (e.g., depositing overlying layers, etching processes, etc.)until arriving at an interest level 210 of the wafer 114, as shown inact 1006 of FIG. 10. For example, one or more levels (e.g., the interestlevel 210 and/or additional overlying layers) may be formed over thereference level 208 and the first set of registration markers 202 of thewafer 114.

Upon arriving at the interest level 210 of the wafer 114, the method1000 may include forming a second set of registration markers 203 on theinterest level 210 of the wafer 114, as shown in act 1008 of FIG. 10.For example, the registration system 100, configured as shown as aphotolithography system, may be used to form the second set ofregistration markers 203 on the interest level 210 of the wafer 114 viaany of the methods described in regard to act 308 of FIG. 3.

Referring still to FIG. 10, when initiating an overlay measurementbetween the reference level 208 and the interest level 210 of the wafer114, the method 1000 may include navigating to a measurement site, asshown in act 1010 of FIG. 10. For instance, the registration system 100may navigate the response sensor 132 over the wafer 114 to a location ofa registration marker 203 of the second set of registration markers 203at a desired measurement site. For instance, the registration system 100may manipulate one or more of the response sensor 132 and the substratesupport 112 via the controller 118 via any of the manners describedabove in regard to FIGS. 1 and 3 to navigate the response sensor 132 tothe measurement site of the wafer 114.

Upon navigating the response sensor 132 to the measurement site of theinterest level 210 of the wafer 114, the method 1000 may includeapplying an external magnetic field to the wafer 114, as shown in act1012 of FIG. 10. In particular, the registration system 100 may apply anexternal magnetic field to at least one registration marker 202 of thefirst set of registration markers 202 within the reference level 208 atthe measurement site of the wafer 114. In some embodiments, theregistration system 100 may apply an external magnetic field to thewafer 114 (e.g., subject the wafer 114 to a magnetic field) via themagnetic source 130 described above in regard to FIG. 1. For example,the registration system 100 may supply a current through a coil of wirewrapped around an iron core to create an external magnetic field. Insome embodiments, the registration system 100 may supply a sufficientamount of current to create an external magnetic field having a strengthgreater than 25 Oe. Moreover, in some embodiments, the magnetic source130 may be disposed within the response sensor 132 of the registrationsystem 100. For instance, the magnetic source 130 may include aninductor. In one or more embodiments, the registration system 100 mayapply external magnetic fields to the wafer 114 on microscales ornanoscales. In some embodiments, applying the external magnetic field tothe wafer 114 is optional. For instance, the registration markers 202may already be magnetized or may be interacting within magnetic fields.

In some embodiments, the registration system 100 may apply an externalmagnetic field to the wafer 114 to magnetize the at least oneregistration marker 202 of the first set of registration markers 202within the wafer 114. Furthermore, in some embodiments, the registrationsystem 100 may drive a magnetization of the at least one registrationmarker 202 of the first set of registration markers 202. As noted above,applying an external magnetic field to ferromagnetic and/orantiferromagnetic materials may cause the at least one registrationmarker 202 of the first set of registration markers 202 to maintain aremanence (e.g., remanent magnetization or residual magnetism).Accordingly, as is discussed in greater detail below, in the second setof embodiments, the registration system 100 may drive a magnetization(e.g., drive an AC magnetic force) of the at least one registrationmarker 202 of the first set of registration markers 202 and may measurea response (e.g., physical force response) based on whether or notmagnetized materials (e.g., one or more of the first set of registrationmarkers 202) are present in the wafer 114.

Upon applying an external magnetic field, the method 300 may includedetermining (e.g., reading) a location of at least one registrationmarker of 202 the first set of registration markers 202 within thereference level 208 of the wafer 114 at the measurement site, as shownin act 1014 of FIG. 10. In some embodiments, determining the location ofthe at least one registration marker of 202 the first set ofregistration markers 202 within the reference level 208 of the wafer 114may include measuring a magnetization of the at least one registrationmarker of 202 the first set of registration markers 202. As used hereinthe term “magnetization” may refer to a density of magnetic dipolemoments that are induced in a magnetic material when the magneticmaterial is placed near a magnet (e.g., the at least one registrationmarker 202). In one or more embodiments, act 1012 (i.e., the act ofapplying a magnetic field) may be repeated during and/or between any ofthe actions taken in act 1014 to maintain and/or drive magnetization ofthe at least one registration marker of 202 the first set ofregistration markers 202.

FIGS. 11 and 12 are schematic representations 1100, 1200 of at least oneregistration marker 202 within a reference level of a wafer 114 and aresponse sensor 132 of a registration system (e.g., registration system100) disposed over the wafer 114. Additionally, FIGS. 11 and 12 showexample scalar magnitudes of magnetizations of the registration markers202 detected via the response sensor 132 when passing the responsesensor 132 over an upper surface 402 of the wafer 114 and above the atleast one registration marker 202 of the first set of registrationmarkers 202 within the wafer 114. As is discussed in greater detailbelow, utilizing data related to the magnetization of a registrationmarker 202 to determine a location of the registration marker 202 deemsvector data unnecessary within the scope of the second set ofembodiments. Referring to act 1016 and FIGS. 10-12 together, theregistration system 100 may pass the response sensor 132 over the uppersurface 402 of the wafer 114 to detect the a magnetization of the atleast one registration marker 202 of the first set of registrationmarkers 202 within the wafer 114. In some embodiments, the registrationsystem 100 may pass the response sensor 132 over the wafer 114 along oneor more of the X-axis, Y-axis, and/or Z-axis of the Cartesian spacedefined above in regard to FIG. 1. For instance, the registration system100 may pass the response sensor 132 along the X-axis to detect amagnitude of the magnetization of the at least one registration marker202 of the first set of registration markers 202 along the X-axis of theCartesian space. As noted above, within the second set of embodiments,the response sensor 132 may include one or more of a MFM probe, SQUID,or VSM.

As a non-limiting example, in embodiments where the response sensor 132includes an MFM probe, the response sensor 132 may include a sharpmagnetized tip for scanning the at least one registration marker 202 ofthe first set of registration markers 202 within the reference level 208of the wafer 114. While passing the response sensor 132 over the wafer114, the registration system 100 may detect interactions between the tipand the at least one registration marker 202 of the first set ofregistration markers 202 (e.g., deflections of the tip). Furthermore,the registration system 100 may utilize data from the interactions toreconstruct the magnetic structure of the at least one registrationmarker 202 of the first set of registration markers 202 (e.g., measuremagnetization of the at least one registration marker 202 of the firstset of registration markers 202). For example, both FIGS. 11 and 12 showmeasured responses (e.g., measured magnitudes of magnetization) acquiredvia the registration system 100.

As another non-limiting example, in embodiments where the responsesensor 132 includes a VSM, the response sensor 132 may include a drivercoil and a search coil, and the process of measuring the magnetizationmay include vibrating (as is known in the art) the at least oneregistration marker 202 of the first set of registration markers 202(e.g., the wafer 114). The driver coil (e.g., a first inductor) may beplaced on a first side of at least one registration marker 202 of thefirst set of registration markers 202, and the search coil (e.g., asecond inductor) may be placed on an opposite second side of the atleast one registration marker 202 of the first set of registrationmarkers 202 forming a circuit. The driver coil may generate a magneticfield and may induce magnetization in the at least one registrationmarker 202 of the first set of registration markers 202 (which may be inaddition to any magnetization already present). Additionally, the atleast one registration marker 202 of the first set of registrationmarkers 202 is vibrated in a sinusoidal motion. A magnetic field isemitted by the at least one registration marker 202 of the first set ofregistration markers 202 due to the magnetization, and the magnetizationof the at least one registration marker 202 of the first set ofregistration markers 202 may be analyzed as changes occur in relation tothe time of the movement (e.g., vibration) of the at least oneregistration marker 202 of the first set of registration markers 202.For instance, magnetic flux changes induce a voltage in the search coilthat are proportional to the magnetization of the registration marker202. The induced voltage may be measured with a lock-in amplifier usinga piezoelectric signal as a frequency reference, as is known in the art.Additionally, as is known in the art, changes in the measured signal(e.g., induced voltage) may be converted to values to determine (e.g.,graph) the magnetization of the at least one registration marker 202 ofthe first set of registration markers 202 versus the magnetic fieldstrength (known in the art as the Hysteresis loop).

In some embodiments, the registration system 100 may pass the responsesensor 132 over the upper surface 402 of the wafer 114 along multipleaxes (e.g., both the X-axis and the Y-axis) of the Cartesian space todetect a magnetization of the at least one registration marker 202 ofthe first set of registration markers 202 along the multiple axes at themeasurement site of the wafer 114.

Referring still to FIG. 10, based on the data acquired via act 1014(e.g., scalar representations of the magnetizations of the registrationmarkers 202 along axes of the Cartesian space), the registration system100 may determine the location of the at least one registration marker202 of the first set of registration markers 202 in three dimensions(e.g., in the X-axis, Y-axis, and Z-axis) within the reference level 208of the wafer 114. For instance, as will be understood by one of ordinaryskill in the art, the registration system 100 may utilize key featuresof known data such as, for example, an expected location of the at leastone registration marker 202 of the first set of registration markers 202within an ideal grid relative to key features of measured data such as,for example, the actual measured field vector and magnetization tensor,minimums, maximums, zero crossing values, 1^(st) and higher orderderivatives, and maximum derivatives of the detected signals (e.g.,magnetizations) to determine a location (e.g., precise location) of theat least one registration marker 202 of the first set of registrationmarkers 202 within the reference level 208 of the wafer 114. As anon-limiting example, if an expected response signal is a sinusoidalresponse (e.g., FIGS. 11 and 12) or other periodic response, theregistration system 100 may utilize the expected response signal and keyfeatures of the measured response signal to determine the actuallocation of the at least one registration marker 202 of the first set ofregistration markers 202.

As is depicted in FIGS. 10-12, determining locations of the at least oneregistration marker 202 of the first set of registration markers 202 bymeasuring magnetization of the at least one registration marker 202 ofthe first set of registration markers 202 may enable the registrationsystem 100 to determine a location of the at least one registrationmarker 202 of the first set of registration markers 202 that may havemagnetic fields that are interacting with each other. Accordingly, bymeasuring magnetization of the at least one registration marker 202 ofthe first set of registration markers 202, the registration system 100may allow for other registration markers to be in close proximity and tohave interacting magnetic fields with the at least one registrationmarker 202 of the first set of registration markers 202 while locatingthe at least one registration marker 202.

In addition to determining a location of the at least one registrationmarker 202 of the first set of registration markers 202 within thereference level 208 of the wafer 114 at the measurement site, the method1000 may include determining a location of at least one registrationmarker 203 of the second set of registration markers 203 on the interestlevel 210 of the wafer 114 at the measurement site, as shown in act 1016of FIG. 10. For instance, the registration system 100 may detect the atleast one registration marker 203 of the second set of registrationmarkers 203 on the interest level 210 of the wafer 114 at themeasurement site via any of the methods described above in regard to act316 of FIG. 3.

Upon determining the locations of the at least one registration marker202 of the first set of registration markers 202 and the at least oneregistration marker 203 of the second set of registration markers 203 atthe measurement site, the method 1000 may include calculating apositional offset between the interest level 210 and the reference level208 of the wafer 114, as shown in act 1018 of FIG. 3. For instance,based on the locations of the at least one registration marker 202 ofthe first set of registration markers 202 within the reference level 208and the at least one registration marker 203 of the second set ofregistration markers 203 within the interest level 210, the registrationsystem 100 may calculate the positional offset (e.g., overlaymeasurement) via any of the methods described above in regard to act 318of FIG. 3.

Additionally, the method 1000 may include adjusting future semiconductorfabrication processes on the wafer 114 or other products based on thecalculated positional offset. For instance, overlay data generated bythe registration system 100 may be used in operating processing tools toadjust future processes such as forming and patterning overlyingmaterials, etching processes, etc. based on the calculated positionaloffset via conventional methods.

The method 1000 may, optionally, include demagnetizing the registrationmarkers, as shown in act 1020 via any of the manners described above inregard to act 320 of FIG. 3.

The method 1000 for aligning a wafer described herein may provide any ofthe advantages described in regard to FIGS. 3-9. Furthermore, becausemethod 1000 functions by detecting and/or measuring the magnetization ofthe first set of registration markers 202 instead of the magneticfields, the method 1000 does not depend on orientations of the magneticmoment of the first set of registration markers 202. For example, method1000 permits arbitrary, while originally known, shapes and placements ofthe first set of registration markers 202 within the wafer 114.Accordingly, method 1000 may be advantageous when shapes and/ororientations of the first set of registration markers 202 are unknownand/or when orienting domains of the first set of registration markers202 is proving difficult.

Third Set of Embodiments

FIG. 13 shows a schematic flow diagram of a method for determining anoverlay measurement between a reference level 208 and an interest level210 of a wafer 114 according to a third set of embodiments of thepresent disclosure. As is described in greater detail below, the thirdset of embodiments may include procedures that involve determining alocation of at least one first registration marker 202 of the first setof registration markers 202 within the reference level 208 of the wafer114 at a measurement site by powering the at least one firstregistration marker with a magnetic field and measuring and/or detectingresponses (e.g., signals, feedback, and/or magnetic fields) from the atleast one first registration marker 202, determining locations of one ormore registration markers 203 of the second set of registration markers203 within the interest level 210 of the wafer 114 at the measurementsite via optical methods, and based on the determined locations of thefirst and second registration markers 202, 203 at the measurement site,calculating a positional offset (e.g., overlay measurement) between theinterest level 210 and the reference level 208 of the wafer 114.

As shown in FIG. 13, similar to method 300 discussed above in regard toFIG. 3, the method 1300 includes creating a first pattern 204 ofrecesses (i.e., a reference level pattern) in a surface (e.g., an uppersurface) of the reference level 208 of the wafer 114 by removingmaterial from the reference level 208 of the wafer 114, as shown in act1302. In some embodiments, recesses of the first pattern 204 viaconventional lithographic processes and methods. For example, the firstpattern 204 of recesses may be formed via any of the methods describedin regard to act 302 of FIG. 3.

As shown in FIG. 13, the method 1300 may further include disposing afirst set of registration markers 202 within recesses of the firstpattern 204 of the reference level 208 of the wafer 114, as shown in act1304 of FIG. 13. Furthermore, in the embodiment of FIG. 13, eachregistration marker 202 of the first set of registration markers 202 mayinclude a circuit configured to be powered via induction. For instance,each registration marker 202 of the first set of registration markers202 may include a receiving inductor for powering the circuit.Additionally, each registration marker of first set of registrationmarkers may include microcircuitry or nanocircuitry or an inductivelypowerable MEMS device operatively coupled to induction-driven powercircuitry.

In one or more embodiments, each registration marker of the first set ofregistration markers 202 may include an antenna. For example, eachregistration marker 202 of the first set of registration markers 202 mayinclude any conventional micro-antennae or nano-antennae. In additionalembodiments, each registration marker 202 of the first set ofregistration markers 202 may include components for producing ACmagnetic fields. For instance, each registration marker of first set ofregistration markers may include one or more solenoids or coils forproducing AC magnetic fields. Additionally, each registration marker ofthe first set of registration markers may be capable of emittingelectromagnetic fields, acoustic vibrations, thermal emissions, and/orother responses (vector or scalar). In some embodiments, the first setof registration markers 202 may include an array of antennae that mayutilize beam shaping and/or other methods to control a directionality ofradiation from the array of antennae. Additionally, the first set ofregistration markers 202 may drive a ferromagnetic core of flux channelthat emits an AC magnetic field.

After the first set of registration markers 202 is disposed within thefirst pattern 204 within the reference level 208 of the wafer 114,additional semiconductor fabrication processes (e.g., depositingoverlying materials, etching processes, etc.) may be effected untilarriving at an interest level 210 of the wafer 114, as shown in act 1306of FIG. 310 For example, one or more substrates (e.g., the interestlevel 210 and/or other overlying layers) may be formed over thereference level 208 and the first set of registration markers of thewafer 114.

Upon arriving at the interest level 210 of the wafer 114, the method1300 may include forming a second set of registration markers 203 on theinterest level 210 of the wafer 114, as shown in act 1308 of FIG. 10.For example, the registration system 100 may be used to form the secondset of registration markers 203 on the interest level 210 of the wafer114 via any of the methods described in regard to act 308 of FIG. 3.

Referring still to FIG. 13, when initiating an overlay measurementbetween the reference level 208 and the interest level 210 of the wafer114, the method 1300 may include navigating to a measurement site, asshown in act 1310 of FIG. 10. For instance, the registration system 100may navigate the response sensor 132 over the wafer 114 to a location ofa registration marker 203 of the second set of registration markers 203at a desired measurement site. For instance, the registration system 100may manipulate one or more of the response sensor 132 and the substratesupport 112 via the controller 118 via any of the manners describedabove in regard to FIGS. 1 and 3 to navigate the response sensor 132 tothe measurement site of the wafer 114.

Upon navigating the response sensor 132 to the measurement site of theinterest level 210 of the wafer 114, the method 1300 may includeapplying an external magnetic field to the wafer 114, as shown in act1312 of FIG. 10. In one or more embodiments, the registration system 100may apply the external magnetic field to an entirety of the wafer 114.In additional embodiments, the registration system 100 may apply theexternal magnetic field to only regions of the wafer 114 (e.g., themeasurement site of the wafer 114). For instance, in some embodiments,the magnetic source 130 may be disposed within the response sensor 132.As a non-limiting example, the magnetic source 130 may include a voltagesource and an inductor. The voltage source may by coupled to theinductor (via traces, wires, etc.) to cause a voltage across theinductor, and as a result, cause the inductor to emit an externalmagnetic field around the inductor. In some embodiments, applying theexternal magnetic field to the wafer 114 is optional. For instance, theregistration markers 202 may already be magnetized or may be interactingwithin magnetic fields.

In response to applying an external magnetic field to the wafer 114,method 1300 may include powering at least one registration marker of thefirst set of registration markers 202 (e.g., at least one circuit)within the wafer 114 at the measurement site, as shown in act 1314 ofFIG. 13. For instance, the inductor of the at least one registrationmarker 202 of the first set of registration markers 202 may create avoltage across the inductor in response to the applied external magneticfield, and the voltage may power the circuit of the at least oneregistration marker 202. Powering the at least one registration marker202 of the first set of registration markers 202 may cause a signal tobe emitted by antenna of the at least one registration marker of thefirst set of registration markers, AC magnetic fields to be emitted by acoil of the at least one registration marker of the first set ofregistration markers, electromagnetic fields to be emitted by a coil ofthe at least one registration marker of the first set of registrationmarkers, acoustic vibrations to be emitted by the at least oneregistration marker of the first set of registration markers, thermalemissions to be emitted by the at least one registration marker, orother responses (vector or scalar) emitted by the at least oneregistration marker of the first set of registration markers 202 anddetectable by the response sensor 132.

Additionally, the method 1300 may include detecting and/or measuring theresponses using response sensor 132 from at least one registrationmarker 202 of the first set of registration markers 202, as shown in act1316 of FIG. 13. For instance, in some embodiments, detecting and/ormeasuring the response from the at least one registration marker 202 ofthe first set of registration markers 202 may include detecting amagnetic field emitted by the at least one registration marker 202 ofthe first set of registration markers 202 via any of the mannersdescribed above in regard to FIGS. 1-12. In additional embodiments,detecting and/or measuring the response from the at least oneregistration marker 202 of the first set of registration markers 202 mayinclude receiving signals (e.g., radiofrequency signals, electromagneticemissions, etc.) from antenna of the at least one registration marker ofthe first set of registration markers. In further embodiments, whereinregistration markers are configured as MEMS devices, vibrations may beinitiated responsive to inductive power, and such vibrations, themagnitude, frequency and waveform thereof, may be detected and measuredby response sensor 132.

Furthermore, based on the detected and/or measured responses from the atleast one registration marker 202 of the first set of registrationmarkers 202, the method 1300 may include determining a location of theat least one registration marker 202 of the first set of registrationmarkers 202 within the reference level 208 of the wafer 114, as shown inact 1318 of FIG. 13. In some embodiments, determining locations of theat least one registration marker of the first set of registrationmarkers within the reference level 208 of the wafer 114 may includedetermining a location of the response sensor 132 over the wafer 114relative to a remainder of the wafer 114. For instance, in operation anduse, the magnetic source 130 may power a circuit within the at least oneregistration marker 202 of the first set of registration markers 202within the wafer 114, and based on the magnitude, location, orientation,etc. of a response from the circuit, the registration system 100 candetermine where the registration marker 202 is located in the wafer 114.

Moreover, the method 1300 may include powering off the at least oneregistration marker 202 of the first set of registration markers 202 viaconventional methods, as shown in act 1320 of FIG. 13. Powering off of aregistration marker 202 of the embodiment may comprise merelyterminating generation of a magnetic field employed as a power source.

In addition to determining a location of the at least one registrationmarker 202 of the first set of registration markers 202 within thereference level 208 of the wafer 114 at the measurement site, the method1300 may include determining a location of at least one registrationmarker 203 of the second set of registration markers 203 on the interestlevel 210 of the wafer 114 at the measurement site, as shown in act 1322of FIG. 10. For instance, the registration system 100 may detect the atleast one registration marker 203 of the second set of registrationmarkers 203 on the interest level 210 of the wafer 114 at themeasurement site via any of the methods described above in regard to act316 of FIG. 3.

Upon determining the locations of the at least one registration marker202 of the first set of registration markers 202 and the at least oneregistration marker 203 of the second set of registration markers 203 atthe measurement site, the method 1300 may include calculating apositional offset between the interest level 210 and the reference level208 of the wafer 114, as shown in act 1324 of FIG. 3. For instance,based on the respective locations of the at least one registrationmarker 202 of the first set of registration markers 202 within thereference level 208 and the at least one registration marker 203 of thesecond set of registration markers 203 within the interest level 210,the registration system 100 may calculate the positional offset (e.g.,overlay measurement) via any of the methods described above in regard toact 318 of FIG. 3.

Additionally, the method 1300 may include adjusting future semiconductorfabrication processes on the wafer 114 based on the calculatedpositional offset. For instance, overlay data from the registrationsystem 100 may be used to by semiconductor processing tools to adjustfuture processes such as forming and patterning overlying materials,etching processes, etc. based on the calculated positional offset viaconventional methods.

FIG. 14 is a schematic representation of a sensor head 1401 that may beutilized with the methods described in regard to FIG. 13. In someembodiments, as described above, the wafer 114 may include an array ofregistration markers 202 within the wafer 114. Furthermore, the sensorhead 1401 may include a complimentary set of markers 1403. For instance,the sensor head 1401 may include an inductive bridge circuit that mayamplify small differences in coupling between two inductor pairs (e.g.,correlating markers between the array of registration markers 202 andthe set of markers 1403 of the sensor head 1401). Additionally, thesensor head 1401 may be utilized via any of the manners described abovein regard to FIG. 13.

Referring to FIGS. 1-14 together, additional embodiments of the presentdisclosure may include metal detector technologies for locatingnon-magnetized registration markers, placing the registration markerswithin die, and unique registration marker designs with fewer designconstraints than conventional, only visually detectable registrationmarkers.

One or more embodiments of the present disclosure include a method ofdetermining an overlay measurement (e.g., a positional offset) betweenan interest level of a wafer and a reference level of the wafer. Themethod may include applying a magnetic field to a wafer, detecting atleast one residual magnetic field emitted from at least one registrationmarker of a first set of registration markers within the wafer,responsive to the detected at least one residual magnetic fields,determining a location of the at least one registration marker of thefirst set registration markers, determining a location of at least oneregistration marker of a second set of registration markers, andresponsive to the determined locations of the at least one registrationmarker of the first set of registration markers and the at least oneregistration marker of the second set of registration markers,calculating a positional offset between an interest level of the waferand a reference level of the wafer.

Some embodiments of the present disclosure include a method ofdetermining an overlay measurement (e.g., a positional offset) betweenan interest level of a wafer and a reference level of the wafer. Themethod may include driving a magnetization of at least one registrationmarker of a first set of registration markers within a reference levelof a wafer, measuring the magnetization of the at least one registrationmarker of the first set of registration markers, responsive to themeasured magnetization of the at least one registration marker of thefirst set of registration markers, determining a location of the atleast one registration marker of the first set of registration markers,determining a location of at least one registration marker of a secondset of registration markers on an interest level of the wafer, andresponsive to the determined locations of the at least one registrationmarker of the first set of registration markers and the at least oneregistration marker of the second set of registration markers,calculating a positional offset between the interest level of the waferand the reference level of the wafer.

One or more embodiments of the present disclosure include a method ofdetermining an overlay measurement (e.g., a positional offset) betweenan interest level of a wafer and a reference level of the wafer. Themethod may include applying a magnetic field to a wafer having a firstset of registration markers disposed within a reference level of thewafer and comprising a ferromagnetic or antiferromagnetic material orany other material or structure capable of interacting with a magneticfield, detecting one or more magnetic attributes of at least oneregistration marker of the first set of registration markers with aresponse sensor, responsive to the detected one or more magneticattributes, determining a location of the at least one registrationmarker of the first set of registration markers, determining a locationof at least one registration marker of a second set of registrationmarkers on an interest level of the wafer, and responsive to thedetermined locations of the at least one registration marker of a firstset of registration markers and the at least one registration marker ofthe second set of registration markers, calculating a positional offsetbetween the interest level of the wafer and the reference level of thewafer.

Further embodiments of the present disclosure include a registrationsystem comprising a substrate support for supporting a wafer, an opticalmicroscope imaging or scatterometry system configured to recognize atleast locations of visible elements on a wafer, a sensor movable overthe wafer and configured to detect magnetic attributes of registrationmarkers within the wafer and a controller operably coupled to thesubstrate support, the sensor and the optical microscope imaging orscatterometry system. The controller comprises at least one processorand at least one non-transitory computer-readable storage medium storinginstructions thereon that, when executed by the at least one processor,cause the controller to: receive data related to detected magneticattributes of the registration markers from the sensor; responsive tothe received data related to detected magnetic attributes, determine atleast locations of the registration markers within the wafer; receivedate related to recognized at least locations of visible elements on awafer; responsive to the received data related to recognized at leastlocations of visible elements, determine at least locations of thevisible elements on the wafer; and responsive to a determined at leastlocations of at least one registration marker and at least one visibleelement, calculate a positional offset between the at least oneregistration marker and the at least one visible element.

The embodiments of the disclosure described above and illustrated in theaccompanying drawings do not limit the scope of the disclosure, which isencompassed by the scope of the appended claims and their legalequivalents. Any equivalent embodiments are within the scope of thisdisclosure. Indeed, various modifications of the disclosure, in additionto those shown and described herein, such as alternate usefulcombinations of the elements described, will become apparent to thoseskilled in the art from the description. Such modifications andembodiments also fall within the scope of the appended claims andequivalents.

What is claimed is:
 1. A method, comprising: applying a magnetic fieldto a wafer; detecting at least one residual magnetic field emitted fromat least one registration marker of a first set of registration markerswithin the wafer; responsive to the detected at least one residualmagnetic fields, determining a location of the at least one registrationmarker of the first set of registration markers; determining a locationof at least one registration marker of a second set of registrationmarkers; and responsive to respective determined locations of the atleast one registration marker of the first set of registration markersand the at least one registration marker of the second set ofregistration markers, calculating a positional offset between aninterest level of the wafer and a reference level of the wafer.
 2. Themethod of claim 1, wherein determining a location of at least oneregistration marker of a second set of registration markers compriseoptically determining the location of the at least one registrationmarker of the second set of registration markers.
 3. The method of claim1, further comprising: forming a first pattern of recesses of a surfaceof the wafer at a reference level; and filling recesses of the firstpattern with a ferromagnetic or antiferromagnetic material to form thefirst set of registration markers.
 4. The method of claim 3, whereinforming a first pattern of recesses in the reference level of the wafercomprises forming the first pattern with each registration marker of thefirst set of registration markers having longitudinal ends aligned alongone of an X-axis, a Y-axis, or a Z-axis of a Cartesian space.
 5. Themethod of claim 1, wherein detecting the at least one residual magneticfield emitted from the at least one registration marker of the first setof registration markers within the wafer comprises detecting the atleast one residual magnetic field with a sensor selected from the groupconsisting of a Hall Effect sensor, a GMR sensor, a TMR sensor, an EMRsensor, or a spin hall sensor.
 6. The method of claim 1, whereinapplying a magnetic field to the wafer comprises applying an in planemagnetic field to the wafer.
 7. The method of claim 1, wherein applyinga magnetic field to the wafer comprises applying an out of planemagnetic field to the wafer.
 8. The method of claim 1, wherein applyinga magnetic field to the wafer comprises rotating all domains within theat least one registration marker of the first set of registrationmarkers to be in known directions.
 9. The method of claim 1, furthercomprising forming the second set of registration markers on a surfaceof the interest level of the wafer.
 10. The method of claim 1, furthercomprising navigating a response sensor to a measurement site of thewafer prior to detecting the at least one residual magnetic fieldemitted from the at least one registration marker of the first set ofregistration markers.
 11. The method of claim 1, further comprisingforming the interest level of the wafer to overlie the reference levelof the wafer after forming the first set of registration markers.
 12. Amethod, comprising: driving a magnetization of at least one registrationmarker of a first set of registration markers within a reference levelof a wafer; measuring the magnetization of the at least one registrationmarker of the first set of registration markers; responsive to themeasured magnetization of the at least one registration marker of thefirst set of registration markers, determining a location of the atleast one registration marker of the first set of registration markers;determining a location of at least one registration marker of a secondset of registration markers on an interest level of the wafer; andresponsive to the determined locations of the at least one registrationmarker of the first set of registration markers and the at least oneregistration marker of the second set of registration markers,calculating a positional offset between the interest level of the waferand the reference level of the wafer within a plane at leastsubstantially parallel to a major surface of the wafer, whereinmeasuring the magnetization of the at least one registration marker ofthe first set of registration markers within the reference level of thewafer comprises measuring the magnetization with a sensor selected froma group consisting of a MFM probe, a SQUID, or VSM.
 13. The method ofclaim 12, further comprising adjusting a semiconductor fabricationprocess based on the calculated positional offset between the interestlevel of the wafer and the reference level of the wafer.
 14. The methodof claim 12, wherein determining a location of at least one registrationmarker of a second set of registration markers comprise opticallydetermining the location of the at least one registration marker of thesecond set of registration markers.
 15. The method of claim 12, whereinmeasuring the magnetization of the at least one registration marker ofthe first set of registration markers comprises: passing a responsesensor over a surface of the wafer at a measurement site; detectinginteractions between a magnetized tip of the response sensor and the atleast one registration marker of the first set of registration markers;and responsive to the detected interactions, determining themagnetization of the at least one registration marker of the first setof registration markers.
 16. A method, comprising: applying a magneticfield to a wafer having a first set of registration markers disposedwithin a reference level of the wafer and comprising a ferromagnetic orantiferromagnetic material; detecting a residual magnetic field of atleast one registration marker of the first set of registration markerswith a response sensor; responsive to the detected residual magneticfield, determining a location of the at least one registration marker ofthe first set of registration markers; determining a location of atleast one registration marker of a second set of registration markers onan interest level of the wafer; and responsive to the respectivedetermined locations of the at least one registration marker of a firstset of registration markers and the at least one registration marker ofthe second set of registration markers, calculating a positional offsetbetween the interest level of the wafer and the reference level of thewafer within a plane at least substantially parallel to a major surfaceof the wafer.
 17. The method of claim 16, further comprising measuring amagnetization of the at least one registration marker of the first setof registration markers.
 18. The method of claim 16, further comprisingapproximating a residual magnetic field of the at least one registrationmarker of the first set of registration markers as a dipole.
 19. Amethod, comprising: applying a magnetic field to a wafer; detecting aresponse from at least one registration marker of a first set ofregistration markers within the wafer; responsive to the detectedresponse, determining a location of the at least one registration markerof the first set of registration markers; determining a location of atleast one registration marker of a second set of registration markers;and responsive to respective determined locations of the at least oneregistration marker of the first set of registration markers and the atleast one registration marker of the second set of registration markers,calculating a positional offset between an interest level of the waferand a reference level of the wafer within a plane at least substantiallyparallel to a major surface of the wafer, wherein detecting the responsefrom the at least one registration marker of the first set ofregistration markers within the wafer comprises detecting the responsewith a sensor selected from a group consisting of a MFM probe, a SQUID,or VSM.
 20. The method of claim 19, wherein detecting a response from atleast one registration marker of a first set of registration markerswithin the wafer comprises detecting photon emissions from the at leastone registration marker of a first set of registration markers.
 21. Themethod of claim 19, wherein detecting a response from at least oneregistration marker of a first set of registration markers within thewafer comprises detecting a DC magnetic field emitted by the at leastone registration marker of a first set of registration markers.
 22. Themethod of claim 19, further comprising disposing the at least oneregistration marker of a first set of registration markers withinrecesses of a pattern within the wafer, the at least one registrationmarker comprising one or more circuits.